Copolyester-carbonate resins are a class of thermoplastic resins that, due to their many excellent mechanical and physical properties, are finding increased use as engineering thermoplastic materials in many commercial and industrial applications. They are a member of the tough thermoplastic family and exhibit excellent properties of toughness, flexibility, impact resistance, heat distortion temperatures, optical clarity, and the like. These copolyester-carbonate resins may generally be prepared, as disclosed in U.S. Pat. No. 3,169,121, by the reaction of a carbonate precursor, a dihydric phenol, and a difunctional carboxylic acid. However, while possessing many advantageous mechanical and physical properties these copolyester-carbonate resins, due to their relatively high melt viscosities, are generally somewhat difficult to process.
It would thus be very advantageous if copolyester-carbonate resin compositions could be provided which while generally retaining, to a generally substantial degree, substantially generally most of their other advantageous properties were simultaneously easier to process. It would be particularly advantageous if copolyester-carbonate resin compositions could be provided which exhibited improved processability and also generally exhibited, to a generally substantial degree, generally relatively good heat distortion temperatures.
It is, therefore, an object of the instant invention to provide copolyester-carbonate resin compositions which exhibit improved processability and also generally exhibit, to a generally substantial degree, generally good mechanical and physical properties.